The regiospecific, high-yield synthesis of 1,4-disubstituted 1,2,3-triazole via an azide-alkyne cycloaddition reaction is of high practical utility as derivatives of this heterocycle are reported to exhibit diverse biological activities. Herein, we demonstrate the development of atomically dispersed copper atoms on graphitic carbon nitride (g-C3N4/Cu) with up to 30% metal loading through a facile one-pot synthesis involving the thermal decomposition of a precursor mix under controlled atmosphere. The EXAFS results established that Cu is atomically dispersed over the g-C3N4 matrix through C-N coordination. The g-C3N4/Cu catalyst with 20 wt % metal loading afforded a variety of 1,4-disubstituted 1,2,3-triazoles in excellent yields in the presence of triethylamine base at 60 degrees C using water as the reaction medium. The triazole synthesis also proceeded well in the absence of an additional base, presumably due to the amino groups of the g-C3N4 matrix. The prepared catalyst exhibited appreciable cyclic stability (>95% yield over 5 cycles) by virtue of the strong metal-support interaction between Cu atoms and the g-C3N4 matrix, preserving the Cu active sites during the reaction cycles. This study demonstrates the development of ultrahigh-density Cu single atoms on g-C3N4 and provides a greener and sustainable pathway for high-yield azide-alkyne cycloaddition reactions.

The development of highly performing Cu-based catalysts with high dispersion of Cu species in nanocrystalline form on a suitable oxide support is significant in reverse water gas shift (RWGS) reaction. We report a simple and robust one-pot sol-gel synthesis of mesoporous Al10-xCuxOy (m gamma-Al10-xCux-SG) catalysts with Cu species in a highly dispersed nanocrystalline form in the gamma-Al2O3 matrix and its high catalytic performance in RWGS reaction. The lack of long range structural order of copper species in m gamma-Al10-xCux-SG catalysts evidenced from Cu-K edge extended X-ray absorption fine structure (EXAFS) studies illustrates the fine distribution of copper species in mesoporous gamma-Al2O3 lattice. Activity study revealed that m gamma-Al10-xCux-SG catalysts showed significantly high CO2 conversion to CO and excellent catalytic stability compared to gamma-Al10-xCux-I prepared by conventional impregnation method. Mesoporous Al9Cu1 (m gamma-Al9Cu1) displayed a CO2 conversion of 45 % at 500 degrees C, which is about 2.8 times higher activity than conventional gamma-Al9Cu1-I catalyst with almost same Cu loading as that of m gamma-Al9Cu1 catalyst. Stability study at 500 degrees C over a period of 50 h revealed that m gamma-Al10-xCux-SG catalysts at low Cu loading (m gamma-Al9.9Cu0.1) showed excellent catalytic stability. The strong copper-alumina interaction in m gamma-Al10-xCux-SG catalysts with enhanced number of active sites at the copper-alumina interface as evidenced from field emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM), H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), electrochemical characterization, and Cu-K edge EXAFS analysis enhances the activity and stability of the catalyst. Density functional theory (DFT) studies and the Operando DRIFTS-MS analysis of RWGS over m gamma-Al9Cu1 catalyst revealed that the mechanism of RWGS reaction to CO formation on m gamma-Al10-xCux-SG catalysts is preceded through the formation of a hydroxycarbonyl (OCOH) intermediate. The present synthesis strategy provides an opportunity for producing Cu-based catalysts with further enhanced activity and stability in RWGS reaction by suitable modification of the catalyst.

This study examines the development of effective passive adsorption materials for NOx removal, with a primary focus on unraveling the dynamics of palladium species impregnated onto zeolite under hydrothermal oxidation conditions. Employing in situ transmission electron microscopy (TEM), the research elucidates the formation of volatile masses at lower temperatures, gradually coalescing during temperature escalation. At the pinnacle temperature of 750 degrees C, a dispersal process ensues, liberating highly mobile smaller particles. The insights garnered from these in situ TEM studies offer an understanding for optimizing and preparing supported noble-metal materials/catalysts, thereby propelling the advancement of materials exhibiting superior performances.

Recent advancements in material science have aimed to create novel nanomaterials with unique properties and potential applications across diverse domains. By deciphering the complexities of the versatile nanomaterial, MgO, the study aims to deepen our comprehension of the synergistic effects induced by dual doping in MgO, thus propelling the advancement of innovative technologies and materials with broad applications. The present investigation employed a facile chemical precipitation and coprecipitation approach to synthesize pure MgO and Ni, Zn dual doped MgO, varying Ni concentration ranging between 2% and 10% and maintaining a constant Zn concentration at 20%. Structural and optical properties were investigated using field emission scanning electron microscope, energy dispersed X-ray analysis, powder X-ray diffraction, absorption spectra, besides photoluminescent analysis. Crystallite size, strain value then dislocation density of the samples were estimated by Scherrer equation and Williamson-Hall method. Tauc plot analysis revealed that codoped samples reduces the bandgap of MgO. The PL emission spectra exhibited a broad emission originating from various defect levels induced by Ni and Zn codoping in MgO. Ferromagnetism was also induced in Ni and Zn codoped samples with a saturation magnetization up to 5.4668 × 10-3 emu for 10%Ni-20%Zn doped MgO. The antibacterial studies were carried out and all samples were effective against the Staphylococcus aureus strain (ATCC 25923). This thorough investigation highlights the multidimensional impact of Ni, Zn dual doping on the characteristics of MgO nanoparticles, offering valuable insights for diverse applications in materials research.

RHO zeolites were synthesized from aluminosilicate gels with sodium and cesium and, optionally, 18-crown-6 ether as a structure directing agent. Phase-pure RHO zeolite samples with different Si/Al ratios and particle morphologies were obtained. In the presence of crown ether phase, pure RHO zeolite was obtained with Si/Al ratios in the range of 3.4-3.8, which appeared as spherical agglomerates of nanosized crystallites. In the absence of crown ether and high-sodium concentration, nanometer-size RHO zeolite with Si/Al ratio of 1.5 and polyhedral morphology was obtained. Lowering the sodium content in the synthesis mixture resulted in crystallization of phase-pure RHO zeolites with Si/Al ratios of 2.8-3.0 with morphologies of spherical agglomerates of tiny crystals next to larger polyhedrons. RHO zeolite samples with a Si/Al ratio as low as 2.8 in their proton form were found to be hydrothermally stable for 3 h at 750 degrees C in air with 12% water vapor, which is exceptional behavior at such a low Si/Al ratio. Crystallinity was maintained despite substantial dealumination. Samples with higher Si/Al ratio showed similar high stability. Loading RHO zeolite with palladium was found to stabilize the zeolite even more because more aluminum was retained in the framework, and dealumination was less pronounced after steam treatment. Pd-loaded RHO zeolite with a Si/Al ratio of 2.8 retained most of its crystallinity after steam treatment for 3 h at 850 degrees C in air with 12% water vapor. The remarkable stability of RHO zeolites at a low Si/Al ratio can be explained by the double eight-rings the framework is composed of. After dealumination by two or even three Al atoms of a double eight-ring it maintains its integrity by the six or five remaining oxide bridges between the two rings.

Selective catalytic reduction (SCR) of NOx by ammonia is one of the dominant pollution abatement technologies for near-zero NOx emission diesel engines. A crucial step in the reduction of NOx to N2 with Cu zeolite NH3-SCR catalysts is the generation of a multi-electron donating active site, implying the permanent or transient dimerization of Cu ions. Cu atom mobility has been implicated by computational chemistry as a key factor in this process. This report demonstrates how variable temperature 1H NMR reveals the Cu induced generation of sharp 1H resonances associated with a low concentration of sites on the zeolite. The onset temperature of the appearance of these signals was found to strongly correlate with the NH3-SCR activity and was observed for a range of catalysts covering multiple frameworks (CHA, AEI, AFX, ERI, ERI-CHA, ERI-OFF, *BEA), with different Si/Al ratios and different Cu contents. The results point towards universal applicability of variable temperature NMR to predict the activity of a Cu-zeolite SCR catalyst. The unique relationship of a spectroscopic feature with catalytic behavior for zeolites with different structures and chemical compositions is exceptional in heterogeneous catalysis.

Palladium exhibits a complex chemistry in the PNA process, especially in the presence of gas mixtures containing CO and NOx. In this work the mechanism of NOx adsorption in gas mixtures with CO, O2 and H2O on a Pd/FER zeolite is investigated. The redox state of palladium and its clustering during high temperature pretreatment and NOx adsorption was investigated. Insight in the chemisorption mechanism was gained by detailed monitoring of the evolution of the NOx and COx concentrations. Oxidized palladium is required for achieving NOx adsorption. Clustered zero-valent palladium reduced with H2 was inactive in presence of O2. Evidence is provided for a reaction mechanism departing from oxygen-bridged PdII-O-PdII moieties of PdO nanoclusters. The NO adsorption site on palladium is obtained by reduction of one of the two PdII atoms to zero valent state which occurs more readily with CO as compared to NO explaining the beneficial role of CO.

Thin hydrophobic polyoligosiloxysilicone (POSiSil) films were synthesized on silicon wafer substrates by spin coating reactive nanometer-sized spherosilicate solutions. Surface roughness was spontaneously induced due to the generation of HCl gas bubbles during the coating procedure, involving the cross-linking and solidification of spherosilicates. Variations in the coating solution and/or relative humidity during the curing phase allowed for a degree of precision in controlling this roughness, thereby impacting parameters such as the porosity and the static contact angle of water on the surface. The introduction of Pluronic 123 into the coating solution, followed by a calcination step after curing, was employed to further augment the surface roughness and porosity. Coatings characterized by uniform foam-like morphologies were synthesized, exhibiting static water contact angles as elevated as 135(degrees). These hydrophobic POSiSil thin films with thicknesses in the nanometer scale have minimal interaction with water, as evidenced by wetting experiments conducted during the ellipsometry. The films also demonstrate the high chemical and thermal stability with no change in the morphology or static contact angle with water. The presence of significant surface area, resulting from the foam-like matrix, coupled with its innate hydrophobic properties and a relatively simple and easily attainable synthesis process, bestows upon the POSiSil coatings considerable potential across a broad spectrum of applications. One noteworthy application includes their use in the detection of volatile organic compounds.

The development of earth-abundant and high-performance bifunctional catalysts for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in alkaline electrolytes is required to efficiently produce hydrogen by electrochemical water splitting, but remains a challenge. We have fabricated mesoporous cobalt iron oxide inverse opals (m-CFO IO) with different mole ratios of cobalt and iron by a wet chemical method using polystyrene beads as a hard template, followed by calcination in air. The performance of the m-CFO IO as OER and HER electrocatalysts was investigated. The as-prepared catalyst with equal concentrations of Fe and Co exhibits remarkable OER and HER performances with low overpotentials of 261 and 157 mV to attain 10 mA cm-2 and small Tafel slopes of 63 and 56 mV dec-1, respectively. An alkaline water electrolyzer with a two-electrode configuration achieves 10 mA cm-2 at 1.55 V with excellent long-term stability, outperforming the combination of noble metal IrO2 and Pt/C benchmark catalysts. The superior catalytic performance is ascribed to the synergistic effects of particle size, crystallinity, oxygen efficiency, a large number of active sites, and the large specific surface area of the porous inverse opal structure.

The photoluminescence properties (PL) of Eu3+ hosted in the hydroxide layers of layered double hydroxides (LDHs) enables calibrationless quantification of anions in the interlayers. The concept is demonstrated during the nitrate-to-carbonate ion exchange in Zn2+/Al3+/Eu3+ LDHs and can be implemented as a remote optical sensor to detect intrusion of anions such as Cl- or CO32-.

A reproducible synthesis strategy for ultracrystalline K,Na-aluminosilicate JBW zeolite is reported. The synthesis uses a Na-based hydrated silicate ionic liquid (HSIL) as a silicon source and gibbsite as the aluminum source. 27Al and 23Na NMR spectra exhibit crystalline second-order quadrupole patterns in the hydrated as well as dehydrated states and distinct resonances for different T-sites demonstrating an exceptional degree of order of the elements of the JBW framework, observed for the first time in a zeolite. Detailed structural analysis via NMR crystallography, combining powder X-ray diffraction and solid-state NMR of all elements (27Al, 29Si, 23Na, 39K, and 1H), reveals remarkable de- and rehydration behavior of the JBW framework, transforming from its as-made hydrated structure via a modified anhydrous state into a different rehydrated symmetry while showing astonishing flexibility for a semicondensed aluminosilicate. Its crystallinity, exceptional degree of ordering of the T atoms and sodium cations, and the fully documented structure qualify this defect-free K,Naaluminosilicate JBW zeolite as a suitable model system for developing NMR modeling methods.

Surface-modified nanoporous silica films offer attractive features for analyte-specific gas detection applications. Here we demonstrate the integration of highly porous silica-alumina films on silicon nanophotonic chips and their performance in selective NH3 detection. Prototype sensors with microporous as well as mesoporous silica films were assembled. The incorporation of aluminum in trace amount needed to generate acid sites was achieved during film deposition or using postsynthesis atomic layer deposition. Silicon photonic micro-ring resonators functionalized with both techniques demonstrated a selective response to NH3 relative to CO2. Furthermore, the response was rapid and reversible. The role of preadsorbed water vapor on the reversible nature of the sensor is also investigated. Experimental observations indicate that water vapor preadsorbed on the films leads to fast sensor recovery while maintaining selectivity toward NH3. This could be attributed to the relatively less strong and still selective binding of NH3 on protonated water molecules preadsorbed on the surface acid sites. The potential of modified nanoporous films for portable and low-cost NH3 sensing on optical chips demonstrated here can be exploited in health care as well as industrial applications.

Owing to their extra-large pores compared to traditional aluminosilicate zeolites, silicogermanates could be attractive for the catalytic transformation of bulky molecules, provided the frameworks can be mod-ified to incorporate acid sites and can be stabilized to survive calcination. Post-synthetic isomorphic sub-stitution of Ge by Si and Al would present a route to achieve this goal. This report describes the transformation and characterization of the non-stable IM-12 silicogermanate into a new stable IZM-7 aluminosilicogermanate by partially substituting Ge by Si in gaseous form to stabilize the material, followed by an aqueous alumination step. IZM-7-based catalyst presents promising performance in the hydroconversion of n-decane compared to conventional zeolites, opening perspectives for the catalytic use of stable derivatives of silicogermanate zeolites. (C) 2021 Elsevier Inc. All rights reserved.

Over the years, COK has developed a family of silicate materials and metal–organic framework hybrids with hierarchical porosity and functionality, coined zeogrids, zeotiles, and COK-x (stemming from the Flemish name of the laboratory “Centrum voor Oppervlaktechemie en Katalyse”). Several of these materials have unique features relevant to heterogeneous catalysis, molecular separation, and controlled release and found applications in the field of green chemistry, environmental protection, and pharmaceutical formulation. Discovery of a new material typically occurs by serendipity, but the research was always guided by hypothesis. This review provides insight in the process of tuning initial research hypotheses to match material properties to specific applications. This review describes the synthesis, structure, properties, and applications of 12 different materials. Some have simple synthesis protocols, facilitating upscaling and reproduction and rendering them attractive also in this respect.

LEV type zeolites were synthesized with four different structure-directing agents and converted to copper loaded NH3-SCR catalysts. The synthesis recipe was found to impact the respective Al population in the two topologically different framework sites in double and single 6-rings, resolvable by 27Al MAS NMR spectroscopy. Hydrothermal stability was found to be related to the silanol concentration, Si/Al ratio, particle size, crystal morphology, crystal defects, external surface area, and microporosity. Catalytic activity in NH3-SCR was dependent on preferential Al siting in the double 6-rings. Levinite synthesized using adamantylamine showed the strongest preference for Al atoms sitting in double 6-ring sites, and showed the highest catalytic turnover frequency. Unfortunately, because of the large crystal size, copper loading of this sample was limited to 0.6 wt% while other samples could be loaded with copper up to 3.3 wt%. An optimum combination of hydrothermal stability and catalytic activity was obtained with N,N'-bis-dimethylpentanediyldiammonium dibromide as structure-directing agent.

Layered double hydroxides (LDHs) serve a score of applications in catalysis, drug delivery, and environmental remediation. Smarter crystallography, combining X-ray diffraction and NMR spectroscopy revealed how interplay between carbonate and pH determines the LDH structure and Al ordering in ZnAl LDH. Carbonate intercalated ZnAl LDHs were synthesized at different pH (pH 8.5, pH 10.0, pH 12.5) with a Zn/Al ratio of 2, without subsequent hydrothermal treatment to avoid extensive recrystallisation. In ideal configuration, all Al cations should be part of the LDH and be coordinated with 6 Zn atoms, but NMR revealed two different Al local environments were present in all samples in a ratio dependent on synthesis pH. NMR-crystallography, integrating NMR spectroscopy and X-ray diffraction, succeeded to identify them as Al residing in the highly ordered crystalline phase, next to Al in disordered material. With increasing synthesis pH, crystallinity increased and the side-phase fraction decreased. Using 1 H- 13 C,  13 C- 27 Al HETCOR NMR in combination with 27 Al MQMAS, 27 Al-DQ-SQ measurements and Rietveld refinement on high-resolution PXRD data, the extreme anion exchange selectivity of these LDHs for CO 3 2- over HCO 3 - was linked to strict Al and CO 3 2- ordering in the crystalline LDH. Even upon equilibration of the LDH in pure NaHCO 3 solutions, only CO 3 2- was adsorbed by the LDH. This reveals the structure directing role of bivalent cations such as CO 3 2- during crystallization of [M 2+4 M3+2 (OH)2 ]2+ [A 2- ] 1 ∙yH 2 O LDH phases.

Remote photocatalytic graphite oxidation proceeds efficiently via a transparent titania photocatalyst thin film coating activating the surface with oxygen functional groups.

γ- and δ-alumina are popular catalyst support materials. Using a hydrothermal synthesis method starting from aluminum nitrate and urea in diluted solution, spherical core-shell particles with a uniform particle size of about 1 μm were synthesized. Upon calcination at 1000 °C, the particles adopted a core-shell structure with a γ-alumina core and δ-alumina shell as evidenced by 2D and 3D electron microscopy and 27Al magic angle spinning nuclear magnetic resonance spectroscopy. The spherical alumina particles were loaded with Pt nanoparticles with an average size below 1 nm using the strong electrostatic adsorption method. Electron microscopy and energy dispersive X-ray spectroscopy revealed a homogeneous platinum dispersion over the alumina surface. These platinum loaded alumina spheres were used as a model catalyst for bifunctional catalysis. Physical mixtures of Pt/alumina spheres and spherical zeolite particles are equivalent to catalysts with platinum deposited on the zeolite itself facilitating the investigation of the catalyst components individually. The spherical alumina particles are very convenient supports for obtaining a homogeneous distribution of highly dispersed platinum nanoparticles. Obtaining such a small Pt particle size is challenging on other support materials such as zeolites. The here reported and well-characterized Pt/alumina spheres can be combined with any zeolite and used as a bifunctional model catalyst. This is an interesting strategy for the examination of the acid catalytic function without the interference of the supported platinum metal on the investigated acid material.

A new zeolite, COK-24, which is an intergrowth of erionite (ERI) and chabazite (CHA), was successfully synthesized for the first time. This was realized via a mixed gel approach. The formation of an intergrowth was confirmed via XRD combined with advanced electron microscopy. The new zeolite intergrowth outperformed its individual counterparts in NH3-SCR reaction.

Controlled chemical functionalization of graphite's outer surface layers into photocatalytically oxidized graphite (POG) is reported. POG can be easily prepared via a UV-driven process using titanium dioxide photocatalyst in molecular oxygen and water vapor at relatively low temperature. The photo-oxidation offers a mild and highly controllable process, providing a chemically tailored POG surface with moderate oxidation degree. Raman spectroscopy is used to directly track the transformation of planar sp(2)-hybridized carbon to oxygenated sp(3)-hybridized chemical functions. Covalent carbon-oxygen bonding at the graphite surface upon oxidation is confirmed by XPS. This vapor-phase process in absence of hazardous liquid chemicals causes oxygen-functionalized and thermally stable POG with an oxygen content up to 14 wt%, suggesting it to be useful for electrocatalysis. Oxidation can be performed with the photocatalyst in direct contact with graphite or mounted at a distance (remote mode). This titanium dioxide-based photocatalytic oxidation is also effective on refractory highly oriented pyrolytic graphite (HOPG). HRSEM and AFM reveal the existence of differently sized surface blisters on natural graphite and HOPG following oxidation. Addition of nitric oxide to the gas mixture accelerates the photoreaction and promptly leads to graphite surface pits and edge erosion due to excessive oxidative strength. (C) 2020 Elsevier Ltd. All rights reserved.